Manufacture of sulphuric acid



Feb. 7, 1933. c. B. CLARK 1,896,287

MANUFACTURE OF SULPHURIC ACID Filed sept. 1o, 1929 vwwtoz CYf/L CMM' @www Y Patented F eb. 7, 1933 .i UNTED STATES MTENT ortica 'v crains. CLARK, or scansnnnn, 'New Yoan, Assicuoa fro cATAvLY-frio rnocnss CORPORATION, or new Yoann. Y., n consola/saxon, or DELAWARE' MAivUFAc'rUnn or sULPHU'nIc Aem Application filed September 10, 1929. Serial N0."391,576.

p My-invention relates more particularly to improved methods for the production of sul-V phuric acid and sulphur trioxide by the con*- tact sulphuric acid process in which the catalyst employed isnot poisoned by the ordinary chloric acid, chlorine, selenium etc. arising from burning or roasting a sulphur containing material as pyrite to produce 'sulphur dioxide. As an example of the type of catalyst preferably used in my methods, I refer to the forms of vanadium catalysts described in the two U. S. patents to Jaeger No.`1,675,308

bers, 1928.

In the customary practice in such contact processes the gases are suitably dried before they pass to the converter system so as to f prevent condensation of sulphuric acidand corrosion of equipment at points in the'sys- ,tem where sulphur trioxide S03 is present with Water vapor, and the temperature is below the condensing point of sulphuric acid. Furthermore the gases are usually dried to aid in absorption of SGB since such gases containing moisture are dificult to absorb.

Heretofore it has been common practice to absorb the SOS in strong sulphuric acid, the Vgases being brought into contact in the final absorption tower with acid of 98-99% strength. It is dicult to maintain the absorbing acid at the exact strength required, and for this reason some of the S03 gas is frequently lost in the Waste gas.

According to my improved methods have eliminated the necessity for drying the gas coming from the burners and also the requirement of maintaining a constant strength acid in the final absorption tower just mentioned. I have discovered new and improved methods for condensing sulphur trioxide (S0-3) from undried gases containing water vapor which is drawn into the burners from the atmosphere under ordinary operating conditions 45. by contacting the SOS Vgas with sulphuricacid vlector and recovered. aseous oisons such. as arsenic h drohaving a higher aqueous vaporpressureethan l 98%acid to partlyabsorb the S03y and .also humidify the balance of theSO3` so thatv it maybe thereafter condensed in amist coly My improved methods` Vof operation are shown in the accompanying drawing in -v which- Y Y f Fig. l is a diagrammatic illustration of the apparatus required for the various inajor55 steps of the process to be carried out when used for the manufacture of fertilizer acid y q nof to 60 Baume. of June 26, 1928 and No. 1,694,123 of Decemi Fig. 2 is a diagrammatic illustration of a modification of the apparatusV shownin' Fig. 60 1,` which is adapted for the production of sulphuric acid of 98% strength or greater. p

Similar reference numerals indicate the .same parts in both figures.V

'f Referringto Fig.ll, the gases 'from the'65 burnerfl Apass through the dust collector 2 and then intothe lirst converter 3 in which 03;. The gas from and 5 are preferably of the self-cleaningtype such as areset forth in my co-pending applicaticnfor patent Serial No. 390,509,1'filed September` 5th, 1929. The small amount of 4dust in the gases issuing from the dust collector 2 is removed in thetwoconverters and; i rI he temperatureof the gas from the con- A verter 5 will be above thecondensation point of 'sulphuric acid, and the fgas is passed at about 600 F. or over directly to thecondens-y ing toweror condenser 6. Acidis circula-ted by the pump 2O over the tower 6to absorb and f condense the greater part of the acid, the acid :being cooledin the cooler 7 toremove the heat from reaction inthe condensation of the S05 in thetowerl y6, and also from the gas. 9 9

It is known that the amount of S03 absorbed depends upon the strength of acid used in the tower 6, other conditions being the same. The relative absorption where a gas containing 5% sulphur trioxide (S08) is used is given approximately as follows Strength Per cent absorbing of SO: ab-

acid sorbed Per ceml With 99%V strength acid inthe tower 6 practically all of the S03 will be absorbed if the gas has been previously dried. When using undried gases, such for example, as contain atleast 5% by volume of S03 and 0.20 pounds of water vapor per'1000 cubic feet of gas, al sulphuric acid inist will be formed in the condenser 6 which will not be absorbed in this condenser. With decreasing strengthsof absorbing `acid in the tower 6, the amount of such inist formed will gradually increase due to the increasing aqueous vapor pressure of the absorbing acid.

Usually it is necessary to produce 98 to 99% acid in the tower 6, and then dilute such acid where a weaker acid is desired; this requires special equipment for cooling the d'ic luted acid. According to my improved methods I make directly the sulphuric acid of the strength desired. y y j For example, if 60o B. acid (77.67%) is desired, I circulate this strength acid over the condensing tower6, and under these conditions about of the S03 will be absorbed and the balance (15%) will-be humidied, and condensed in the mist collector 8 from which such recovered acid is returned to the cooler 7 and added to the acid in circulation `in the tower 6. Water is added to such acid in circulation as required to maintain-such acid 4at the desired strength. The acid product as made is drawn off. from the cooler 7, and the fan 9 acts to draw the gas through the system as shown. l According to my improved process as described and shown in Fig. 1, any strength acid up to 98% strength can be produced, and the customary steps of drying the gases from the burner, and then diluting the absorbing acid to make the product of the required strength are dispensed with.

A modification of this process which is particularly adapted for the production of sulphuric acid of greater strength than 98% is diagrammatically shown in Fig. 2.

A strongl acid condenser 10 is placed in the line between the converter 5 and the. weak acid condenser 6. 0 leum`is circulated over this condenser tower 10 and cooler 11 by the 'which burner gases into contact with sulphuricA acid ofpredeterinined strengthin circulation pump 12 by which the oleum absorbs a part of the sulphur .trioxide (S03), while weak acid from the condenser 6 passes from the cooler 7 through the pipe 13 to dilute the acid made on the condenser 10. By such methods oleum of various grades can be produced and then drawn ott from the cooler 11. The gas from theconverters 3 and 5 will contain at least 5% by volume of S03, and also water vapor to the extent of about 0.20 lbs. or more per 1000 cubic feet of gas. The cooler 14; is placed between the 4vconverter 5 and ycondenser to partially cool the oncoming gas,

and weak acid productmay be drawn volif from the cooler 7 as in the Fig. 1 apparatus,

if desired.

I claim as vmy invention: 1. In the manufacture of sulphuric acid from undried burnergases, the steps in conwhich comprise contacting such undried'V` burner gases with sulphuric acid of predetermined strength to partly absorb the sulphur trioxide,humidifying substantially all the unabsorbed sulphur trioxide and condensing same to acid, and returning such condensed acid directly to the acid of predetermined strength. i

3. In a. manufacture of'sulphuric acid from undried burner gases, the steps in condensing sulphur trioxide trom said gases which coni-fA prise contacting such undried burner gases with sulphuric acid of predetermined strength to partly absorb the sulphur trioxide, humidifying substantially all the unabsorbed sulphur trioxide and condensing saine to acid, and diluting and returning such condensed acid directly to the acid of predetermined strength.

4. In the manufacture of sulphuric acid from undried burner gases, the steps in condensng sulphur trioxide from said gases which comprise bringing such undried burner gases into contact with sulphuric acid of predetermined strength in circulation to partly absorb the sulphur trioxide, humidifying substantially all the unabsorbed sulphur trioxide and condensing same to acid, and returning such condensed acid directly to the acid in circulation.

5. In the manufacture of sulphuric acid i from undried burner gases, the steps in condensing sulphur trioxide from said gases comprise bringing such undried to partly absorb the sulphur trioxide, humidifying substantially all the unabsorbed sulphur trioXide and condensing same to acid, and diluting and returning such condensed acid directly to the acid in circulation to maintain the acid in circulation at predetermined strength.

6. In the manufacture of sulphuric acid from undried burner gases, lthe steps in condensing sulphur trioXide from said Ygases which comprise contacting such undried burner gases with sulphuric acid having a higher aqueous vapor pressure than 98% acid, and humidifying substantially all the unabsorbed sulphur trioxide and condensing same to acid.

7. In the manufacture of sulphuric acid, the process for condensing sulphur trioxide from undried gases containing at least 5% 2u by volume of S03 and 0.20 pounds of Water vapor per 1000 cubic feet, which comprises contacting said undried gases With sulphuri'c acid in circulation having a higher aqueous vapor pressure than 98% acid to partly absorb sulphur trioxide, and humidifying sub-k stantially all the unabsorbed sulphur trioXide and condensing same to acid.

8. ln the manufacture of sulphuric acid, the process for condensing sulphur trioXide 3o from undried gases containing at least 5% by volume of SOS and 0.20 pounds of Water vapor per 1000 cubic feet, which comprises contacting said undried gases` With sulphuric acid in circulation having a higher aqueous vapor pressure than 98% acid to partly absorb sulphur trioxide, humidifying substantiaily all the unabsorbed sulphur trioXidev and condensing same to acid, and returning the condensed acid to the acid in circulation. 40 9. ln the manufacture of sulphuric acid, the process for condensing sulphur trioXide from undried gases containing at least 5% by volume of SOS and 0.20 pounds of Water vapor per 1000 cubic feet, which comprises contacting said undried gases With sulphuric acid in circulation having a higher aqueous vapor pressure'than 98% acid to partly absorb sulphur trioxide, humidifying substan-V tially all the unabsorbed sulphur trioXide and 5o condensing same to acid, and diluting and returning the condensed acid to the acid in cir-` culation. l0. In the manufacture of sulphuric acid of more than 98% strength from undried burner gases, the steps in condensing sulphur trioXidefrom said gases which comprise contacting such gases with oleum in circulation to absorb part of the sulphur trioxide, contacting the balance of sulphur trioxide with relatively Weak acid to condense same, and returning such condensed acid to dilute n the strong acid produced from the oleum in circulation.

' CYRIL B. CLARK. 

